Physical exam was non-contributory. Chest imaging revealed a 1.5 cm2 smoothly marginated, non-calcified, non-cavitary left upper lobe pulmonary nodule (Fig. 1). A surveillance bronchoscopy with brushing was negative for malignancy. Despite this, a repeat computed tomography (CT) scan six months after the bronchoscopy identified the lesion to be increasing to 2.3 cm2. Other than a mildly appreciable left superhilar lymph node, the mediastinal structures were unremarkable. This, concurrent with a 30 lb weight loss over the same period, prompted the patient to undergo a left thoracic

wedge resection of the left lung. Areas of necrotizing granulomatous inflammation with PJP cysts were identified on histopathology (Fig. 2). No other pathogens,

including aerobic organisms, acid-fast bacilli or other fungal species were Cell Cycle inhibitor in either the bronchoalveolar lavage or biopsy. No other pathologic features were apparent. PJP cysts were not present on an expectorated sputum sample collected two days later. An extensive workup was initiated to elicit obvious immunodeficiencies buy SCR7 in the patient given that PJP is not expected in an immunocompetent host. She tested negative for HIV-1&2 (by enzyme EIA assay and P24 antigen), HTLV-1&2, hepatitis B and C. Serum immunoglobulins (IgG, IgM, IgA, IgE), lymphocyte subpopulation count (CD3, CD4, CD8), collagen vascular disease markers (ANA, Rheumatoid factor, GBM antibody, ANCA, anti-MPO, PR3) and malignancy investigation (CT of chest and abdomen) were all within normal limits. She had an ability to mount an appropriate immune response, as evidenced by the presence of IgG antibodies for mumps and rubella, diphtheria and tetanus, suggesting appropriate vaccination against such diseases. Laboratory test for complement C3, complement C4, alpha-1 Ribonucleotide reductase antitrypsin, anti-actin were normal. While initially no treatment was provided, a lingering cough prompted a course of trimethoprim-sulfamethoxazole (TMP/SMZ) DS 800/160 mg two

tablets by mouth thrice daily for three weeks. Symptoms resolved and did not recur through eighteen months of observation nor did any new syndrome to suggest undiagnosed immunodeficiency. Follow up radiographic imaging did not show evidence of recurrence. PJP is a type of pneumonia originating from the fungus Pneumocystis jiroveci, which is specific to humans [1]. PJP antibodies can be serologically present in the absence of symptoms and histopathology findings in healthy individuals suggest that Pneunocystis jiroveci is an opportunistic pathogen of ubiquitous distribution and low pathogenicity. Immunocompetent individuals with asymptomatic colonization of pneumocystis have the potential to transmit the fungus to others including immunocompromised individuals [2]. PJP normally presents as an interstitial pneumonia.